[cflsystems]

The file is skin1/customer/main/product_details.tpl and the code to comment out

{if $product.weight ne "0.00" || $variants ne ''}
<tr id="product_weight_box"{if $product.weight eq '0.00'} style="display: none;"{/if}>
<td class="property-name">{$lng.lbl_weight}</td>
<td class="property-value" colspan="2">
<span id="product_weight">{$product.weight|formatprice}< /span> {$config.General.weight_symbol}
</td>
</tr>
{/if}